For most automobiles, it is necessary to periodically change the cooling liquid in the cooling system of the engine. When coolant is changed, it is preferable to flush out the entire system so as to rinse away the contaminants or solid particles thay may have accumulated in the cooling system.
Mechanics have found it convenient in the past to insert a fitting into one of the heater hose lines so that a special connecting hose of a flushing machine in the shop may be connected to the heater hose with the effect that water may be circulated through the engine and radiator for flushing the entire system. Such fittings have previously been T-shaped fittings, the opposite ends of which are connection into the heater hose, and the center or T connection is a threaded socket fitting or male thread upon which a cap is normally mounted and which is attachable to such a flushing machine.
These prior known T fittings have presented numerous problems for the casual backyard mechanic because the discharge end of a conventional garden hose will not properly fit onto the prior heater hose T fittings.